This small fly like insect lays its eggs in the leaves of boxwoods. Dwarf English, American and Asian boxwoods are susceptible to varying degrees. Treatment must include proper timing of foliar insecticides and the use of systemic insecticides.
Once the eggs hatch inside the leaf, the larvae eat the plant tissue. The damaged leaves appear discolored and blistered. The larvae emerge once they have 
matured. The damaged leaves may stay on the plant for some time before abcising.